Field
The present method and system relates generally to a digital communication system and more particularly to the use of error correcting codes in digital communications systems, and particularly relates to the use of LDPC (low density parity check) codes in digital communications systems. Examples of such systems include digital television broadcast systems, cellular telephone systems and the like.
Description of the Related Art
Like all linear block codes, an LDPC (low density parity check) code can be described in terms of a matrix. In the case of an LDPC code the matrix contains a first portion consisting of information bits and a second portion containing parity bits, the matrix commonly being referred to as an H-matrix, or a parity check matrix. The LDPC code gets its name from the H-matrix which contains relatively few 1's in comparison to the number of 0's.
Many modern communications systems require the use of error correction codes that can accommodate different code rates and different lengths of information bits. It is well known that longer code lengths improve error correcting performance, while shorter code lengths are characterized by reduced processing delays. Likewise it is known that increasing code rates improves the data rate and bandwidth efficiency, while reducing code rates increases information robustness in noisy channels. However, designing separate error correction codes for each different code length and code rate that may be used in a particular communications system is a very complicated process and often not practical.
It would therefore be highly desirable to provide a novel error correction system using error correction codes capable of adapting to different information lengths and different code rates. Such a system would be designed with the goal of providing performance that is equal or close to the performance of systems using separately designed codes and would inherently be of low complexity since it would obviate the need to design a separate code for each condition and would employ encoder and decoder hardware that can be reused in different situations without extra cost.